1. Field of the Invention
This invention relates to a blade driving apparatus for cameras in which each of a shutter device, a stop device, and a filter device is constructed as an independent unit, or at least two of them are constructed as one unit.
2. Description of Related Art
A lens shutter device (hereinafter referred to as a shutter device), a stop device, and a filter device, in recent years, incorporated in a camera have blade members so that they are reciprocated by an electromagnetic driving source (an actuator such as a motor or a plunger). Such shutter devices are often designed so that two shutter blades are rotated in opposite directions. However, some of the shutter devices incorporated in cameras of extremely small lens diameters, including cameras for mobile phones, are constructed with a single shutter blade.
Recently, stop devices incorporated in cameras of relatively small lens diameters have come to be used only for the purpose of controlling the amount of light. Some of the stop devices are constructed so that a plurality of stop blades are actuated simultaneously to restrict a plurality of stop apertures. In many cases, however, the stop devices are such that a single stop blade having an aperture section for a circular stop aperture is provided and is introduced into, and removed from, an exposure aperture when the necessity arises. The stop device of such a type may include a plurality of stop blades that are different in diameter of the aperture section.
Filter devices, in many cases, are provided with a blade member similar in shape to the stop blade having the circular aperture section (however, the aperture section may have almost the same size as the exposure aperture) so that an ND filter plate is mounted on the blade member to cover the aperture section in the proximity of the aperture section and thereby is constructed as a filter blade. In some of the filter devices, however, two blade members having such circular aperture sections are provided and a blade member fabricated only with the ND filter plate is held between them so that these three members are rotated and returned in the same direction simultaneously as if they were a single blade. The filter device of this type may include a plurality of filter blades in which aperture sections are different in diameter or ND filter plates are different in density.
As mentioned above, the shutter device, the stop device, and the filter device in which the shutter blade, the stop blade, and filter blade are actuated by the electromagnetic driving source may be individually unified, but two or more devices may be constructed as one unit. Even when they are individually unified, an opening shutter blade and a closing shutter blade may be actuated by independent electromagnetic driving sources in the shutter device. In some of the stop devices, as mentioned above, the plurality of stop blades different in diameter of the aperture section are actuated by independent electromagnetic sources. In some of the filter devices, the plurality of filter blades in which aperture sections are different in diameter or ND filter plates are different in density are actuated by independent electromagnetic driving sources. In the case of the blade driving apparatus for cameras provided with two kinds of blade members actuated by independent electromagnetic sources, the two kinds of blade members may be arranged in the same blade chamber, but may be placed in separate blade chambers.
In addition to being used in digital cameras provided with solid-state image sensors, such as digital still cameras, digital video cameras, monitoring cameras, and cameras for information communication end devices, various types of blade driving apparatuses for cameras unified as mentioned above can be used in conventional silver-halide film cameras and video cameras. Of these devices, shutter devices of extremely preferred structures in which the slim design of the entire unit is attained by reducing the dimension of the electromagnetic driving source in the direction of the optical axis are set forth in Japanese Patent Kokai Nos. 2003-186079 and 2004-32873.
In various types of blade driving apparatuses for cameras mentioned above, as well as in the shutter devices constructed as the description in Kokai Nos. 2003-186079 and 2004-32873, it is common practice to mount the electromagnetic driving source, such as the motor, to one surface of a base plate and the blade to the other surface. Thus, when an operator holds the base plate with his hand to carry out assembly work, handling of components including the base plate becomes very cumbersome. Alternatively, when the operator places the base plate on a work bench (also called an assembly tool) to do the assembly work, he must turn the base plate inside out, and thus at least two kinds of work benches for exclusive use become necessary. This is unfavorable in view of manufacturing costs.
The electromagnetic driving sources disclosed in Kokai Nos. 2003-186079 and 2004-32873, in contrast with those set forth, for example, in Japanese Patent Kokai Nos. 2002-139765 and 2003-5251, are capable of reducing dimensions in the direction of the optical axis, irrespective of the same kind of electromagnetic driving source in function, and have favorable structures for the slim design of the entire apparatus. However, even in the case of the electromagnetic driving source of the type set forth in each of Kokai Nos. 2003-186079 and 2004-32873, a plate member is required to place a rotor between one surface of the base plate and the plate member and must be made relatively thick for the purpose of protecting the blade driving apparatus in treatment such as carrying. Consequently, in order to incorporate the blade driving apparatus in an ultra slim design camera, a further consideration is required.